IntegrityError: columns csid, mapping are not unique

[Martin Pool]

I just tested tip of bzr and bzr-hg and got

% ./bzr -Dhttp -Derror branch http://spyderlib.googlecode.com/hg/ /tmp/test
bzr: ERROR: sqlite3.IntegrityError: columns csid, mapping are not unique

Traceback (most recent call last):
  File "/home/mbp/bzr/trunk/bzrlib/commands.py", line 826, in exception_to_return_code
    return the_callable(*args, **kwargs)
  File "/home/mbp/bzr/trunk/bzrlib/commands.py", line 1027, in run_bzr
    ret = run(*run_argv)
  File "/home/mbp/bzr/trunk/bzrlib/commands.py", line 638, in run_argv_aliases
    return self.run(**all_cmd_args)
  File "/home/mbp/bzr/trunk/bzrlib/builtins.py", line 1249, in run
    source_branch=br_from)
  File "/home/mbp/bzr/trunk/bzrlib/bzrdir.py", line 1184, in sprout
    result_repo.fetch(source_repository, fetch_spec=fetch_spec)
  File "/home/mbp/bzr/trunk/bzrlib/repository.py", line 1703, in fetch
    find_ghosts=find_ghosts, fetch_spec=fetch_spec)
  File "/home/mbp/bzr/trunk/bzrlib/decorators.py", line 194, in write_locked
    result = unbound(self, *args, **kwargs)
  File "/home/mbp/.bazaar/plugins/hg/fetch.py", line 645, in fetch
    self.addchangegroup(cg, mapping)
  File "/home/mbp/.bazaar/plugins/hg/fetch.py", line 524, in addchangegroup
    self._add_inventories(todo, mapping, pb)
  File "/home/mbp/.bazaar/plugins/hg/fetch.py", line 388, in _add_inventories
    rev.properties['manifest'], rev.foreign_revid, mapping)
  File "/home/mbp/.bazaar/plugins/hg/idmap.py", line 229, in insert_revision
    self.db.execute("insert into revision (revid, csid, manifest_id, mapping) values (?, ?, ?, ?)", (revid, changeset_id, manifest_id, str(mapping)))
IntegrityError: columns csid, mapping are not unique
./bzr -Dhttp -Derror branch http://spyderlib.googlecode.com/hg/ /tmp/test 6.18s user 0.36s system 36% cpu 17.691 total